Radios

The first radio is next to your contact, J.B. If you start running (hold your Context Action button), you went too far ahead.

The second radio is after you make your first "moral choice" in regards to J.B. After the plane crashes into the building, the radio is visible just before you open the next gate.

The third radio is the gate control room above where the Shotgun Heavy appears (from the level exit). Note that just outside the window from the radio is a weapon part.

Mission 2

The first radio is where you have the co-op surrender tutorial and cut-scene.

The second radio is after you make your way down the skyscraper (on different sides). Enemies near a PMC strongbox will allow you do another mock surrender; the radio is near the strongbox.

Mission 3

The first radio is right after you rescue the first group of hostages (past the gate). Check the side-alley (or workshop area) for the radio before you encounter a cut-scene for the second group of hostages.

The second radio is in the zoo's loading dock (after the ambush) and before you enter the zoo proper. If you activated the zoo's tram, you just screwed yourself.

Mission 4

The first radio is in the basement where the generator is in. Can't miss it unless your eyes have melted off your face from the Call of Cthulhu spell Strike Blind or you injected your eyeballs with sulphuric acid.

The second radio is in the hallway right the step-jump with the kid at the hospital, and before the hostages in the surgery theater.

Mission 5

The first radio is next to the PMC strongbox after battling the APC, Flamethrower Super Heavy, and Shotgun Heavy in the first alley.

The second radio is in the alleyway when Alice Murray contacts T.W.O. a second time about going to the shopping mall.

Mission 6

The first radio is at the start of the stage.

The second radio is by the PMC strongbox at the second underground checkpoint.

Mission 7

The last radio is in the hallway after battling the Mini-Gun Super Heavy (on the stairs) but before you enter the next small courtyard with the emplaced gun.